This invention is in the field of plant molecular biology. More specifically, this invention pertains to nucleic acid fragments encoding hexose carrier proteins in plants and seeds.
In plants, there is a compartmentation of metabolism between the cytosol and the plastid; the chloroplast envelope is in part responsible for this compartmentalization. This envelope or membrane selectively transports free hexose sugars including D-glucose, D-fructose and D-ribose. Hexose carrier proteins, situated in the chloroplast membrane, are responsible for controlling the flux of carbon, in the form of hexose sugars, across the envelop. Hexose carrier proteins may be used to manipulate carbohydrate transport and may be used to alter carbon partioning in the whole plant or to manipulate carbohydrate distribution between cellular compartments.
No corn, rice, sorghum, soybean, or wheat genes have been reported for any hexose carrier protein. Accordingly, the availability of nucleic acid sequences encoding all or a portion of these enzymes would facilitate studies to better understand carbohydrate metabolism and function in plants, provide genetic tools for the manipulation of these biosynthetic pathways, and provide a means to control carbohydrate transport and distribution in plant cells.
The instant invention relates to isolated nucleic acid fragments encoding hexose carrier proteins. Specifically, this invention concerns an isolated nucleic acid fragment encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein. In addition, this invention relates to a nucleic acid fragment that is complementary to the nucleic acid fragment encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein. An additional embodiment of the instant invention pertains to a polypeptide encoding all or a substantial portion of a corn, rice, sorghum, soybean or wheat hexose carrier protein.
In another embodiment, the instant invention relates to a chimeric gene encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein, or to a chimeric gene that comprises a nucleic acid fragment that is complementary to a nucleic acid fragment encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein, operably linked to suitable regulatory sequences, wherein expression of the chimeric gene results in production of levels of the encoded protein in a transformed host cell that is altered (i.e., increased or decreased) from the level produced in an untransformed host cell.
In a further embodiment, the instant invention concerns a transformed host cell comprising in its genome a chimeric gene encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein, operably linked to suitable regulatory sequences. Expression of the chimeric gene results in production of altered levels of the encoded protein in the transformed host cell. The transformed host cell can be of eukaryotic or prokaryotic origin, and include cells derived from higher plants and microorganisms. The invention also includes transformed plants that arise from transformed host cells of higher plants, and seeds derived from such transformed plants.
An additional embodiment of the instant invention concerns a method of altering the level of expression of a corn, rice, sorghum, soybean or wheat hexose carrier protein in a transformed host cell comprising: a) transforming a host cell with a chimeric gene comprising a nucleic acid fragment encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein; and b) growing the transformed host cell under conditions that are suitable for expression of the chimeric gene wherein expression of the chimeric gene results in production of altered levels of hexose carrier protein in the transformed host cell.
An addition embodiment of the instant invention concerns a method for obtaining a nucleic acid fragment encoding all or a substantial portion of an amino acid sequence encoding a corn, rice, sorghum, soybean or wheat hexose carrier protein.